1. Field of the Invention
The subject invention generally pertains to a device and method for restraining a truck from accidentally moving away from a loading dock, and more specifically to engaging an ICC bar of a truck.
2. Description of Related Art
When a truck backs against a loading dock, it can be important to restrain the truck from accidentally moving too far away from the dock while loading or unloading the truck. This is often accomplished by a hook-style vehicle restraint that grabs what is often referred to in the industry as an ICC bar or a Rear Impact Guard (RIG). An ICC bar or RIG is a bar or beam that extends horizontally across the rear of a truck below the truck bed. It helps prevent an automobile from under-riding the truck in a rear-end collision.
To effectively restrain the truck, it can be desirable to control the position of the vehicle restraint relative to the ICC bar. This can be difficult, since the height and shape of ICC bars vary among trucks. Moreover, the height can vary with just one truck as weight is added or removed from the truck while at the loading dock.
This problem is addressed in the vehicle restraint described in U.S. Pat. No. 4,264,259. The vehicle restraint employs springs to position and maintain a carriage up against the underside of a truck's ICC bar. Once the carriage is properly positioned, a drive motor rotates a hook into engagement with the bar. Although effective, the '259 device requires two drive mechanisms: one for the carriage and a second for rotating the hook. The carriage is biased into a raised position by the springs, while the hook is motor driven.
Another device that addresses the issue of aligning a vehicle restraint to an ICC bar is disclosed in U.S. Pat. No. 4,759,678. The apparatus has an air cylinder that pushes directly against a hook to lift the hook upward. A carriage essentially hanging from the hook rises with it, until the carriage meets an obstruction. If the obstruction happens to be a properly positioned ICC bar, the hook continues to rise out of the carriage to form a barrier to horizontal movement of the bar.
Although the '678 vehicle restraint accommodates vertical position variations of ICC bars, it overlooks at least one horizontal position that could be dangerously unsafe. In particular, if an ICC bar was to catch the forward-most tip of carriage 12, beyond hook 32, hook 32 can still rise, and limit switch 47 will indicate that the truck is hitched when it actually is not. Also, any debris or ice binding carriage guide 13 could allow hook 32 to extend before carriage 12 was even close to an ICC bar. Again, such a situation would trip limit switch 47 to indicate that the truck is safely hitched when it actually was not. Similarly, it also appears that the device could indicate that an ICC bar was safely restrained if the carriage simply reached the end of its travel at item 11 without engaging an ICC bar. Moreover, if the hook and carriage were inadvertently left at their upward position as a truck backed into the dock, the truck's ICC bar may hit the exposed cylinder rod. It appears that such an impact could easily cause extensive damage to a relatively delicate rod.